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by ejolson
Mon Jan 25, 2016 7:45 pm
Forum: General discussion
Topic: Why is ARM so cheap, and x86 so expensive?
Replies: 91
Views: 34206

Re: Why is ARM so cheap, and x86 so expensive?

I've recently been looking at small single-board computers that come with x86 processors, for a few reasons. One is I'd like a minimalistic computer that does everything my normal computer does (including running Windows-only software) except with cheaper running costs. I'd also like to run some ol...
by ejolson
Sun Jan 24, 2016 4:17 pm
Forum: General discussion
Topic: Obfuscation thread
Replies: 34
Views: 4647

Re: Obfuscation thread

I put thought and effort into my posts to this thread and find it discouraging that you have found it a pain to preserve the meaningful replies on the subject of code obfuscation and copy protection. The original post was serious and received reasonable advice that he and others including myself may...
by ejolson
Sat Jan 23, 2016 6:09 pm
Forum: C/C++
Topic: Creating Script to Log "top" Command Output
Replies: 8
Views: 1204

Re: Creating Script to Log "top" Command Output

You say you want a "script" yet you've posted this in the C/C++ forum. C and C++ are not scripting languages, they are compiled languages. Having seen how much memory and CPU some resource monitoring deamons written in interpreted languages use, it seems like a good idea to write a simple one in C ...
by ejolson
Thu Jan 21, 2016 10:24 pm
Forum: Off topic discussion
Topic: Minecraft for Education Coming Summer 2016 for $5/£3.50
Replies: 9
Views: 1713

Re: Minecraft for Education Coming Summer 2016 for $5/£3.50

So over a student's time in school, cheaper to buy a Pi2 with Minecraft, Python, and so much more. And you don't need a traditional PC. (I'll ignore the cost of peripherals, they are the same for Pis and for traditional PCs). Assuming a Pi will last 3 years and can be used by 5 students each year, ...
by ejolson
Thu Jan 21, 2016 7:09 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

<SNIP> but you may want to search the web for this. As you've continued this thread well beyond your original post, it seems likely you will eventually succeed in getting your Pi cluster to work. This will certainly require quite a bit of self study and searching on Google. So you knock me for sayi...
by ejolson
Thu Jan 21, 2016 6:51 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

LMGTFY Aha! Let me Google that for you to discover what LMGTFY means. Sometimes, people aren't certain what they need to learn in order to get started. This is why, for example, people go to school. Why university degrees have specific course requirements. And why it might be unwise to let a studen...
by ejolson
Thu Jan 21, 2016 1:58 am
Forum: Off topic discussion
Topic: Minecraft for Education Coming Summer 2016 for $5/£3.50
Replies: 9
Views: 1713

Re: Minecraft for Education Coming Summer 2016 for $5/£3.50

Microsoft has announced that it will be releasing an educational version of Minecraft during Summer 2016 for $5/£3.50 per student. It will emphasize building STEM and computing skills as well as blocky worlds, and licenses will work both on school computer systems and at home. I find it interesting...
by ejolson
Wed Jan 20, 2016 11:55 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

Ben_is_best wrote:I tried

Code: Select all

sudo apt-get install openmpi
, but it said

Code: Select all

Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package openmpi
Any suggestions?
How about

Code: Select all

apt-get install openmpi-bin libopenmpi-dev
by ejolson
Mon Jan 18, 2016 8:35 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

I've made the cluster, so now how do you combine the processing power to make a supercomputer? The standard API to harness the parallel processing power of a cluster for supercomputing applications is MPI. The package OpenMPI should be available in the Raspbian repositories. Except for speed, a clu...
by ejolson
Sun Jan 17, 2016 6:31 pm
Forum: Teaching and learning resources
Topic: Learning about linux(not shell)
Replies: 20
Views: 3990

Re: Learning about linux(not shell)

I thought maybe I should learn about the Linux itself, not like how to use it, but how it works, how i can alter it and etc... For example i learned about Linux kernel, drivers and sysfs from using my raspberry pi, but I want to know more, I googled and found nothing, mostly because i had no idea w...
by ejolson
Sun Jan 17, 2016 5:55 pm
Forum: General discussion
Topic: Good FTP server?
Replies: 10
Views: 49872

Re: Good FTP server?

Here are some copy tests; SSH - 3 Mbps Proftp - 6Mbps Vsftp - 7Mbps Pure-ftp - 8Mbps So yes, SSH is an option but a slow option, I would still rather go with ftp if its for internal use. The communications slowdown caused by encryption is related to the network speed versus the CPU speed. Any conne...
by ejolson
Fri Jan 15, 2016 5:29 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

I am at a loss to understand, especially since the worst was ZERO to ZERO in "Gadget" Mode.... Zero to Zero communication must pass through the 2B. Specifically, every packet from the first Zero is sent to the 2B which then forwards it to the other Zero. Thus, it is not surprising that Zero to Zero...
by ejolson
Thu Jan 14, 2016 5:13 pm
Forum: General discussion
Topic: Ethernet/USB bottleneck
Replies: 23
Views: 6913

Re: Ethernet/USB bottleneck

Hi Guys, As per my previous post, Was wondering if anyone had tried a 5ghz 801.11ac Wi-Fi dongle, and seen if this provides more performance over USB than a LAN cable using a 100mbit connection? As WiFi is a broadcast medium where every connected device interferes with every other, putting the Pi o...
by ejolson
Thu Jan 14, 2016 6:41 am
Forum: General discussion
Topic: Ethernet/USB bottleneck
Replies: 23
Views: 6913

Re: Ethernet/USB bottleneck

NTFS needs to go. Agreed. NTFS is bad news. I would not be surprised if switching from NTFS to EXT4 gave a 50 percent improvement in file server performance. However, if you are streaming video and don't have enough bandwidth, the usual solution is to stream video at lower resolution and bit rates.
by ejolson
Thu Jan 14, 2016 6:31 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

I am at a loss to understand, especially since the worst was ZERO to ZERO in "Gadget" Mode.... Zero to Zero communication must pass through the 2B. Specifically, every packet from the first Zero is sent to the 2B which then forwards it to the other Zero. Thus, it is not surprising that Zero to Zero...
by ejolson
Mon Jan 11, 2016 6:23 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

fruitoftheloom wrote:110 Mbits/sec
These numbers seem much better compared to
mikerr wrote:37.6 Mbits/sec
I wonder if it is the USB cable or the Lubuntu PC instead of a Pi2B that made the difference.
by ejolson
Sun Jan 10, 2016 6:56 pm
Forum: Staffroom, classroom and projects
Topic: Setup Pi Internet through school proxy
Replies: 13
Views: 10490

Re: Setup Pi Internet through school proxy

Hello, Can anyone tell me how to configure a pi2 to use a proxy server to access the internet. As we are setting up a class of pi's we need internet connectivity on each pi, however we have to configure the browser to use a proxy. Have searched this forum and others but have yet to find clear guida...
by ejolson
Sun Jan 10, 2016 4:43 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

While one might have hoped for a faster than 200 mbps interconnect... Hi ejolson - how do you expect to get 200 Mbps through an Ethernet interface that only has a 100 Mbps maximum theoretical instantaneous bit rate capatility? As a gigabit Ethernet dongle connected through USB obtains 220 mbps , on...
by ejolson
Sun Jan 10, 2016 8:20 am
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

It will work fine, up to a theoretical maximum of 10Mbps. You may also have limits on the number of simultaneous TCP connections (not sure, it has been a while since I read the data sheet) I am wondering, why nobody is speaking of networking Zeros with an enc28j60 SPI2ETH chip, making use of GPIO (...
by ejolson
Sat Jan 09, 2016 10:33 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

zero to zero: [ ID] Interval Transfer Bandwidth [ 4] 0.0-10.2 sec 52.8 MBytes 43.3 Mbits/sec Does not seem particularly speedy, but at least it works :D From my point of view creating a cluster using only a Pi B+ and three Pi zeros without any additional networking hardware is an amazing success. W...
by ejolson
Fri Jan 08, 2016 5:38 pm
Forum: General discussion
Topic: 2 node raspberry pi supercomputer
Replies: 71
Views: 14243

Re: 2 node raspberry pi supercomputer

mikerr wrote:Hmm - my skills are failing me with multiple pizeros :?
Any progress with zero to zero communication?
by ejolson
Wed Jan 06, 2016 7:20 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4090

Re: Webserver

Round here the worst, slowest, cheapest domestic internet connections I have seen for five years or more are 10Mb/s down and 20 or more up (Yes, outgoing faster than incoming) Free with the rent or maybe 10 Euro a month. Strangely enough 20 mbps is the fastest upstream domestic connection mentioned...
by ejolson
Wed Jan 06, 2016 6:55 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4090

Re: Webserver

150MB/s sounds great. I'm on their cheapest option, only 50Mb/s down. Have you tried something like http://www.speedtest.net to check that out? Yep, I've done that too. Is this upstream or downstream or both? Some services only advertise the downstream, which can be 10 to 50 times faster than upstr...
by ejolson
Wed Jan 06, 2016 12:40 am
Forum: General discussion
Topic: adding minimal GUI X windows to Jessie Lite
Replies: 2
Views: 18869

Re: adding minimal GUI X windows to Jessie Lite

I'm running fvwm on my Pi, which is light weight compared to most window managers. I think something like # apt-get install fvwm xterm xserver-org x11-apps might be enough to get started. After logging in start the window manager using xinit or startx depending on whether you want to use xauth cooki...
by ejolson
Tue Jan 05, 2016 9:22 pm
Forum: General discussion
Topic: Webserver
Replies: 31
Views: 4090

Re: Webserver

BTW, encryption can easily chew up an order of magnitude of bitrate, especially if it's being done in software, which is usually much worse. I get about 94 mbps between a Pi 2B and a Linux PC using iperf. This is pretty close to the theoretical 100 mbps hardware maximum. A Pi should be able to util...

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